Source Code
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These source-code files are part of a reconstructed copy of Luminary 69/2,
the flown, final release of the Apollo 10 Lunar Module (LM) Apollo Guidance Computer (AGC) software.
The reconstruction is based on the source code of Luminary 69 — i.e., the
initial, unflown version, "revision 0" — of which
a contemporary listing was available. The code was then updated by incorporating the
differences between Luminary 69 and Luminary 69/2, known from other contemporary
documentation. The only such difference is the implementation in
Luminary 69/2 of the "R-2 Lunar Potential Model", the source code for which was taken
from program Luminary 99/1 (Apollo 11 LM), of which a contemporary listing was also available.
Finally, the now-reconstructed Luminary 69/2 was then validated by assembling it to
executable form and verifying that its memory banks had the correct checksums,
known from still other contemporary documentation.
Note that page numbers in the reconstructed code match those in the original Luminary 69
program listing, or in the ORBITAL INTEGRATION log section, in Luminary 99/1. Page numbers
would certainly differ somewhat in a contemporary Luminary 69/2 listing.
Moreover, annotations that were not present in the contemporary source code have been added
to the reconstructed code to justify each change in Luminary 69/2 relative to
Luminary 69. Here's a guide to the Apollo documentation referenced in those annotations:
Comments from the original source code are prefixed with a single '#' symbol,
whereas comments added later are prefixed by "##" or "###". Report any errors
noted by creating an
issue report at the Virtual AGC
project's GitHub repository.
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034831,000002: ## Copyright: Public domain.
034832,000003: ## Filename: THROTTLE_CONTROL_ROUTINES.agc
034833,000004: ## Purpose: A section of LUM69 revision 2.
034834,000005: ## It is part of the reconstructed source code for the flown
034835,000006: ## version of the flight software for the Lunar Module's (LM)
034836,000007: ## Apollo Guidance Computer (AGC) for Apollo 10. The code has
034837,000008: ## been recreated from a copy of Luminary revsion 069, using
034838,000009: ## changes present in Luminary 099 which were described in
034839,000010: ## Luminary memos 75 and 78. The code has been adapted such
034840,000011: ## that the resulting bugger words exactly match those specified
034841,000012: ## for LUM69 revision 2 in NASA drawing 2021152B, which gives
034842,000013: ## relatively high confidence that the reconstruction is correct.
034843,000014: ## Reference: pp. 797-801
034844,000015: ## Assembler: yaYUL
034845,000016: ## Contact: Ron Burkey <info@sandroid.org>.
034846,000017: ## Website: www.ibiblio.org/apollo/index.html
034847,000018: ## Mod history: 2019-07-27 MAS Created from Luminary 69.
034848,000019:
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Page 797
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034850,000021:
034851,000022: 31,2247 BANK 31
034852,000023: 31,2000 SETLOC FTHROT
034853,000024: 31,2000 BANK
034854,000025: 31,2247 E7,1610 EBANK= PIF
034855,000026: 31,2247 COUNT* $$/THROT
034856,000027:
034857,000028: # * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
034858,000029: # HERE FC, DESIRED THRUST, AND FP, PRESENT THRUST, UNWEIGHTED, ARE COMPUTED.
034859,000030:
034860,000031: 31,2247 31246 THROTTLE CA ABDELV # COMPUTE PRESENT ACCELERATION IN UNITS OF
034861,000032: 31,2250 00006 EXTEND # 2(-4) M/CS/CS, SAVING SERVICER TROUBLE
034862,000033: 31,2251 72444 MP /AF/CNST
034863,000034: 31,2252 00006 +3 EXTEND
034864,000035: 31,2253 23605 QXCH RTNHOLD
034865,000036: 31,2254 02425 AFDUMP TC MASSMULT
034866,000037: 31,2255 53563 DXCH FP # FP = PRESENT THRUST
034867,000038: 31,2256 00006 EXTEND
034868,000039: 31,2257 31574 DCA /AFC/
034869,000040: 31,2260 02425 TC MASSMULT
034870,000041: 31,2261 55613 TS FC # FC = THRUST DESIRED BY GUIDANCE
034871,000042: 31,2262 53561 DXCH FCODD # FCODD = WHAT IT IS GOING TO GET
034872,000043:
034873,000044: # IF IT HAS BEEN LESS THAN 3 SECONDS SINCE THE LAST THROTTLING, AUGMENT FP USING THE FWEIGHT CALCULATED THEN.
034874,000045:
034875,000046: 31,2263 41615 CS TTHROT # THIS CODING ASSUMES A FLATOUT WITHIN
034876,000047: 31,2264 60025 AD TIME1 # 80 SECONDS BEFORE FIRST THROTTLE CALL
034877,000048: 31,2265 74733 MASK POSMAX
034878,000049: 31,2266 40000 COM
034879,000050: 31,2267 65002 AD 3SECS
034880,000051: 31,2270 00006 EXTEND
034881,000052: 31,2271 62275 BZMF WHERETO # BRANCH IF (TIME1-TTHROT +1) > 3 SECONDS
034882,000053: 31,2272 00006 EXTEND
034883,000054: 31,2273 31607 DCA FWEIGHT
034884,000055: 31,2274 21563 DAS FP
034885,000056:
034886,000057: # THIS LOGIC DETERMINES THE THROTTLING IN THE REGION 10% - 94%. THE MANUAL THROTTLE, NOMINALLY SET AT
034887,000058: # MINIMUM BY ASTRONAUT OR MISSION CONTROL PROGRAMS, PROVIDES THE LOWER BOUND. A STOP IN THE THROTTLE HARDWARE
034888,000059: # PROVIDES THE UPPER.
034889,000060:
034890,000061: 31,2275 35014 WHERETO CA EBANK5 # INITIALIZE L*WCR*T AND H*GHCR*T FROM
034891,000062: 31,2276 54003 TS EBANK # PAD LOADED ERASABLES IN W-MATRIX
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Page 798
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034893,000064: 31,2277 E5,1476 EBANK= LOWCRIT
034894,000065: 31,2277 00006 EXTEND
034895,000066: 31,2300 31477 DCA LOWCRIT
034896,000067: 31,2301 52131 DXCH L*WCR*T
034897,000068: 31,2302 35016 CA EBANK7
034898,000069: 31,2303 54003 TS EBANK
034899,000070: 31,2304 E7,1610 EBANK= PIF
034900,000071: 31,2304 44755 CS ZERO # INITIALIZE PIFPSET
034901,000072: 31,2305 55604 TS PIFPSET
034902,000073: 31,2306 40131 CS H*GHCR*T
034903,000074: 31,2307 61616 AD FCOLD
034904,000075: 31,2310 00006 EXTEND
034905,000076: 31,2311 62323 BZMF LOWFCOLD # BRANCH IF FCOLD < OR = HIGHCRIT
034906,000077: 31,2312 40130 CS L*WCR*T
034907,000078: 31,2313 61560 AD FCODD
034908,000079: 31,2314 00006 EXTEND
034909,000080: 31,2315 62320 BZMF FCOMPSET # BRANCH IF FC < OR = LOWCRIT
034910,000081: 31,2316 31562 CA FP # SEE NOTE 1
034911,000082: 31,2317 12337 TCF FLATOUT1
034912,000083:
034913,000084: 31,2320 42002 FCOMPSET CS FMAXODD # SEE NOTE 2
034914,000085: 31,2321 61562 AD FP
034915,000086: 31,2322 12341 TCF FLATOUT2
034916,000087:
034917,000088: 31,2323 40131 LOWFCOLD CS H*GHCR*T
034918,000089: 31,2324 61560 AD FCODD
034919,000090: 31,2325 00006 EXTEND
034920,000091: 31,2326 62342 BZMF DOPIF # BRANCH IF FC < OR = HIGHCRIT
034921,000092:
034922,000093: 31,2327 30102 CA FLAGWRD6 # IS POUTFLAG SET?
034923,000094: 31,2330 74745 MASK POUTBIT
034924,000095: 31,2331 00006 EXTEND
034925,000096: 31,2332 12336 BZF FLATOUT1 -1
034926,000097:
034927,000098: 31,2333 30131 CA H*GHCR*T # YES: THROTTLE-UP ONLY TO HIGHCRIT
034928,000099: 31,2334 55560 TS FCODD
034929,000100: 31,2335 12342 TCF DOPIF
034930,000101:
034931,000102: 31,2336 32003 CA FMAXPOS # NO: THROTTLE-UP
034932,000103: 31,2337 53561 FLATOUT1 DXCH FCODD
034933,000104: 31,2340 34737 CA FEXTRA
034934,000105: 31,2341 55604 FLATOUT2 TS PIFPSET
034935,000106:
034936,000107: # NOTE 1 FC IS SET EQUAL TO FP SO PIF WILL BE ZERO. THIS IS DESIRABLE
034937,000108: # AS THERE IS ACTUALLY NO THROTTLE CHANGE.
034938,000109:
034939,000110: # NOTE2 HERE, SINCE WE ARE ABOUT TO RETURN TO THE THROTTLEABLE REGION
034940,000111: # (BELOW 55%) THE QUANTITY -(FMAXODD-FP) IS COMPUTED AND PUT
034941,000112: # INTO PIFPSET TO COMPENSATE FOR THE DIFFERENCE BETWEEN THE
034942,000113: # NUMBER OF BITS CORRESPONDING TO FULL THROTTLE (FMAXODD) AND THE
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Page 799
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034944,000115: # NUMBER CORRESPONDING TO ACTUAL THRUST (FP). THUS THE TOTAL
034945,000116: # THROTTLE COMMAND PIF = FC - FP - (FMAXODD - FP) = FC - FMAXODD.
034946,000117:
034947,000118: 31,2342 03721 DOPIF TC FASTCHNG # RESTART PROTECTION
034948,000119: 31,2343 00006 EXTEND
034949,000120: 31,2344 31561 DCA FCODD
034950,000121: 31,2345 55616 TS FCOLD
034951,000122: 31,2346 53611 DXCH PIF
034952,000123: 31,2347 00006 EXTEND
034953,000124: 31,2350 41563 DCS FP
034954,000125: 31,2351 21611 DAS PIF # PIF = FC - FP, NEVER EQUALS +0
034955,000126:
034956,000127: 31,2352 31610 DOIT CA PIF
034957,000128: 31,2353 61604 AD PIFPSET # ADD IN PIFPSET, WITHOUT CHANGING PIF
034958,000129: 31,2354 55612 TS PSEUDO55
034959,000130: 31,2355 54055 TS THRUST
034960,000131: 31,2356 34750 CAF BIT4
034961,000132: 31,2357 00006 EXTEND
034962,000133: 31,2360 05014 WOR CHAN14
034963,000134: 31,2361 30025 CA TIME1
034964,000135: 31,2362 55615 TS TTHROT
034965,000136:
034966,000137: # SINCE /AF/ IS NOT AN INSTANTANEOUS ACCELERATION, BUT RATHER AN "AVERAGE" OF THE ACCELERATION LEVELS DURING
034967,000138: # THE PRECEEDING PIPA INTERVAL, AND SINCE FP IS COMPUTED DIRECTLY FROM /AF/, FP IN ORDER TO CORRESPOND TO THE
034968,000139: # ACTUAL THRUST LEVEL AT THE END OF THE INTERVAL MUST BE WEIGHTED BY
034969,000140:
034970,000141: # PIF(PPROCESS + TL) PIF /PIF/
034971,000142: # FWEIGHT = ------------------ + -------------
034972,000143: # PGUID 2 PGUID FRATE
034973,000144:
034974,000145: # WHERE PPROCESS IS THE TIME BETWEEN PIPA READING AND THE START OF THROTTLING, PGUID IS THE GUIDANCE PERIOD, AND
034975,000146: # FRATE IS THE THROTTLING RATE (32 UNITS PER CENTISECOND). PGUID IS ASSUMED TO BE 2 SECONDS. THE "TL" IN THE
034976,000147: # FIRST TERM REPRESENTS THE ENGINE'S RESPONSE LAG. HERE FWEIGHT IS COMPUTED FOR USE NEXT PASS.
034977,000148:
034978,000149: 31,2363 35003 CA 4SECS
034979,000150: 31,2364 54002 TS Q
034980,000151: 31,2365 41235 CS PIPTIME +1 # TIME OF LAST PIPA READING
034981,000152: 31,2366 60025 AD TIME1
034982,000153: 31,2367 62004 AD THROTLAG # COMPENSATE FOR ENGINE RESPONSE LAG
034983,000154: 31,2370 74357 MASK LOW8 # MAKE SURE SMALL AND POSITIVE
034984,000155: 31,2371 22007 ZL
034985,000156: 31,2372 00006 EXTEND
034986,000157: 31,2373 10002 DV Q
034987,000158: 31,2374 00006 EXTEND
034988,000159: 31,2375 71610 MP PIF
034989,000160: 31,2376 60000 DOUBLE
034990,000161: 31,2377 53607 DXCH FWEIGHT
034991,000162: 31,2400 37715 CA 2.PG.FRT
034992,000163: 31,2401 54002 TS Q
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Page 800
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034994,000165: 31,2402 11610 CCS PIF
034995,000166: 31,2403 64753 AD ONE
034996,000167: 31,2404 12406 TCF +2
034997,000168: 31,2405 64753 AD ONE
034998,000169: 31,2406 00006 EXTEND
034999,000170: 31,2407 71610 MP PIF
035000,000171: 31,2410 00006 EXTEND
035001,000172: 31,2411 10002 DV Q
035002,000173: 31,2412 22007 ZL
035003,000174: 31,2413 21607 DAS FWEIGHT
035004,000175:
035005,000176: 31,2414 01605 THDUMP TC RTNHOLD
035006,000177:
035007,000178: # FLATOUT THROTTLES UP THE DESCENT ENGINE, AND IS CALLED AS A BASIC SUBROUTINE.
035008,000179:
035009,000180: 31,2415 34737 FLATOUT CAF BIT13 # 4096 PULSES
035010,000181: 31,2416 55604 WHATOUT TS PIFPSET # USE PIFPSET SO FWEIGHT WILL BE ZERO
035011,000182: 31,2417 44755 CS ZERO
035012,000183: 31,2420 55616 TS FCOLD
035013,000184: 31,2421 55610 TS PIF
035014,000185: 31,2422 00006 EXTEND
035015,000186: 31,2423 23605 QXCH RTNHOLD
035016,000187: 31,2424 12352 TCF DOIT
035017,000188:
035018,000189: # MASSMULT SCALES ACCELERATION, ARRIVING IN A AND L IN UNITS OF 2(-4) M/CS/CS, TO FORCE IN PULSE UNITS.
035019,000190:
035020,000191: 31,2425 00006 MASSMULT EXTEND
035021,000192: 31,2426 22130 QXCH BUF
035022,000193: 31,2427 00006 EXTEND
035023,000194: 31,2430 71244 MP MASS # LEAVES ODDLY SCALED FORCE IN A AND L
035024,000195: 31,2431 52155 DXCH MPAC
035025,000196: 31,2432 07102 TC DMP # LEAVES PROPERLY SCALED FORCE IM MPAC
035026,000197: 31,2433 02005 ADRES SCALEFAC
035027,000198: 31,2434 07256 TC TPAGREE
035028,000199: 31,2435 30154 CA MPAC
035029,000200: 31,2436 00006 EXTEND
035030,000201: 31,2437 12442 BZF +3
035031,000202: 31,2440 34733 CAF POSMAX
035032,000203: 31,2441 00130 TC BUF
035033,000204: 31,2442 52156 DXCH MPAC +1
035034,000205: 31,2443 00130 TC BUF
035035,000206:
035036,000207: # CONSTANTS:-
035037,000208:
035038,000209: 31,2444 4737 FEXTRA = BIT13
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Page 801
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035040,000211: 31,2444 7715 2.PG.FRT = PRIO31 # DECIMAL 12800
035041,000212: 31,2444 04143 /AF/CNST DEC .13107
035042,000213:
035043,000214: # * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
End of include-file THROTTLE_CONTROL_ROUTINES.agc. Parent file is MAIN.agc